Numerous types of roof assemblies have previously been proposed for pre-engineered buildings in efforts to provide a watertight roof assembly, while also enabling the roof assembly to expand and contract as changes in temperature are encountered. One such prior art roof assembly of considerable success in recent years is the standing seam roof assembly.
The panel members of a standing seam roof assembly are joined along lapped together side edges forming the standing seams. The panel members are secured to secondary structural members by either clips or through fasteners. The clips used to attach the standing seam are of two types: floating (one or two piece moveable); and fixed (one piece with no movement allowed between the panel and the supporting structure). Through fasteners, when employed, penetrate the panels and attach the panels to underlying support structure to substantially lock the panels and support structure together so that differential movement is restricted. Roofs may be classified as shed roofs and sloped gasket roofs. Shed roofs shed water because gravity pulls the water down and away from panel joints more effectively than wind or capillary action propel water thought the joint. Shed roofs generally occur over slopes of three to twelve or greater. Sloped gasket roofs, on the other hand, provide roof joints that are made watertight by placing gasket material between the panel joints and securing the gasket material in place by, for example, encapsulating or exerting pressure on the gasket material such as by seaming. Generally, sloped gasket roofs have a ¼ to twelve slope or greater.
Heretofore, field seamed gasket joints in large roofs have generally been limited to two-piece clips in which movement between the roof and the underlying structure occurred within the clip. The reason for this is that, in the past, the top hook portion of the clip intersected the gasket sealant, and if the clip hook moved in relation to the panel which held the sealant, the movement of the clip hook deformed and destroyed the gasket seal. Single piece clips have been used freely in small and shed roofs where gasket sealing is not required.
If floating clips or flexible framing are not used, the repeated action of expansion and contraction of the panel member tend to weaken the panel-to-panel lap joints and the panel to framing connection, causing separation, structural failure and roof leakage. Leaks are generally caused by the weakening of the fastening members and working or kneading of the sealant disposed at the joints. Thus, sealants for such roof assemblies have required the qualities of adhesion, flexibility and water repellence. Further, in many instances the pressure on the sealant can vary greatly throughout the length of the sidelap and end lap joints of the panels, resulting in uneven distribution and voids in the joint sealant.
Many of the problems encountered with prior art standing seam roofs, such as structural failures and leaks, are overcome by the standing seam floating roof assembly taught by U.S. Pat. No. 5,737,894 issued to Harold G. Simpson and Leo E. Neyer. The standing seam floating roof assembly is formed of elongated metal panels, each of which is provided with a female member formed along one longitudinal edge and a male member formed along the opposed longitudinal edge. Adjacently disposed panels are joined by interlocking female and male members to form the standing seam joint. Clips interconnect the standing seam joints and the supporting structure, with the upper portions of the clips hooking over the male members of the panels. Most such clips are of the sliding type which permit the hooking portions to move relative to supporting base portions connected to the supporting structure, while relative motion between the clip hooks and the metal panels is substantially prevented. A sealant material is disposed to form a moisture dam in the interlocking joints of the female and male members.
In addition to standing seam roof assemblies used in newly constructed pre-engineered buildings, standing seam roof assemblies are also finding increased usage in another segment of the roofing industry, that of the replacement of built-up roofs. Generally, a built-up roof is formed of a plurality of interconnected sections that are sealed by a watertight over coat of asphaltic composition. Such built-up roofs have generally performed well, but problems can be expected with age; from building settlement; and from standing water pockets resulting from construction errors. Standing water usually results in deterioration of the roof, resulting in leaks and other problems.
There remains a need for improved standing seam roof assembly having improved integrity of strength and water tightness performance.